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Mar 12, 2014

A dual side electroluminescence measurement system for LED wafer manufacturing

The development of a system that evaluates the performances
of an LED (light-emitting diode) waferusing a non-destructive
test method after crystal growth and before chip processing is presented. The
system measures electroluminescent characteristics of two sides of an epi-wafer.
When a probe makes contact with an epi-wafer, a source meter drives an electric
current, then emits LED light. Optical characteristics were measured
by two spectrometers and two pico-am meters. The measured data were peak
wavelength, FWHM (full width at half maximum), forward current, forward voltage
and reverse current. The measuring devices are installed on the front and rear
of the wafer. The probe and measuring devices were transferred by a 3-axis
stage for the EL contact. Mapping images of the epi-wafer were obtained
using these characteristics. The correlation between wafer state and
chip state, and repeatability for an epi-wafer, were considered in the test.